Upon knowing that a person can have only one Sadguru, a doubt could now crop up in the mind. ‘Does it imply that other Gurus are not worthy of worship? Should I not respect them or serve them? Are they not Mahatmas?’
Let me answer this- Yes, all Gurus are Mahatmas. This is true. You can respect all of them. You can prostrate before them. Nevertheless, you must believe that all of these Gurus are manifestation of your Guru! With this feeling, you can respect them and even offer Guru seva.
However, when it comes to obtaining initiation, you must necessarily approach only your Guru. You have to progress only on that Sadhana path into which your Guru had initiated you. The only restriction is that you cannot take initiation from other Gurus. After taking initiation from one Guru, you can respect other Mahatmas who come into your life, but you cannot take initiation from them again.
Remember that the path preached by your Guru is the right one for you. If the path preached by other Gurus is similar to the one preached by your Guru, you can abide by it- ‘Oh this is similar to what my Guru preaches. It is very nice’. Thus you can appreciate the teachings of others that are similar to the teachings of your Guru.
But when the teaching is different then you cannot say, ‘What is this? How could my Guru not teach me this?’ or ‘Ah, so what, my Guru will bound to teach this to me some other day’. Both such attitudes are inacceptable! The first one reflects ego and the second lax attitude. Both are inacceptable and wrong.
To be frank, to a true aspirant, every atom in this world is his Guru. Every atom preaches him. Is it not true that Datta had 24 Gurus? It is stated in the Datta Purana. More importantly, a Guru studies the individual need of every disciple and, based on this, He will initiate the disciple into a specialized path suited to him/her.
Therefore, remember that when having the darshan of any great Mahatma, the disciple should think that his own Guru has come in this new form. He should not treat the Mahatma as yet another Guru of his. He should not seek Yantras and Mantra-initiation from Him.
Only when the Sadguru discards this human body or permanently disappears into the Himalayas without giving any instructions or when the Guru explicitly sends you to another Guru, you can approach another Guru and seek discipleship under him. This is the rule per shastras.